You can also store an e-card in your Apple Wallet and add funds to it the same way (transferring on the gift card website). That way, you can use your phone or an Apple Watch to "tap to pay" and it will deduct the funds from your gift card. The only bummer is that the balance does not update so it will only show the original balance of the card that you load. You would have to check the website or your receipts to see the current balance.